Electrical Troubleshooting Quiz

Discuss this Article 10

Anonymous (not verified)

on Feb 26, 2013

If a standard motor starter is utilized for the motor control, vs. a VFD, consider checking for proper coil voltage and proper contactor engagemnet strength. If correct, be sure to check for wear and burning on the contacts themselves. Do to normal arcing and wear contacts may become carboned and will limit proper voltage through the contact creating increased amperage.

If you have access to a good thermal imager usit it to scan the electrical connections. We had a situation where we were blowing the fuses in the MCC for a motor but not blowing the smaller fuses in the local disconnect. We found that a loose connection in the MCC was causing the problem. Unce the connection was cleanes and tightened the problem went away.

Verify the pressure is acurate you could be starting against a higher pressure in the recieving tank which could intermittently cause the fuses to blow. The pressure switch could be bad or out of calibration.

You stated that you have 200hp motor, need more info, name plate,voltage, amps, hp, three phase? Letter? Etc. motor type, wire size? Then we can determine and come up with a solution. Using 2011 NEC -NFPA
Thanks louconstant

Based on the information already submitted I would also check the power factor and see if power factor correction is faulty or necessary. A 200HP motor is a large load to be starting across the line. I definitely would use a VFD or soft-start device for that large of motor regardless. If you have test equipment a power quality analyzer measuring the start up wave-shapes would provide valuable information as to the problem by indicating uniformity, voltage and current magnitude, angle, etc.

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